The solution when using a consumer camera is to switch
out of auto mode and set it to “aperture priority mode” or
“manual mode” in order to use the smallest aperture for the
available light. The best solution, however, is to use a tilt/
shift lens or a view camera that allows for tilting the area of
sharp focus along the plane of the subject. The key to getting
everything in focus is using enough light, smaller apertures
and camera movements to control depth of field. Shots with a
blurry background that fades to nothing should generally be
avoided in flexographic printing.
Factor: Digital Blurriness
Digital photos require sharpening because the nature of
digital imaging is, frankly, blurry. These images appear blurry
because of the way that pixels manifest themselves when the
edges of subjects cut across pixels. The white background is
recorded as white and the black image is recorded as black.
Individual pixels cannot record the object’s edges as half
black and half white, so they record gray tones that soften the
edges of the object.
solution: sharpening
Sharpening is needed to fix digital blurriness and to make
the edges appear sharp again. Sharpening filters make dark
edges darker and light edges lighter by increasing contrast
along the edges of objects. It is either done automatically as a
part of the camera’s programming, or after taking the shot in
an image-editing program.
Sharpening in post-processing is preferred. The best
results are obtained when sharpened by a color specialist
who understands what happens to images when they are
printed.Control is necessary to determine how much sharpen-
ing is enough, which programs to use, what size to view the
photo when sharpening and how large to make the sharpen-
ing lines. If the shot is in focus and there is enough detail,
texture and resolution, the sharpening filter has something
to grab onto and can make the photo look razor sharp. Most
Prosumer cameras have built-in sharpening features that can
be controlled, so these settings should be turned off so that
photos are not sharpened twice.
every little Bit helps... or can hurt
Scaling, setting color neutrals, setting white-points and
black-points, and CMYK conversion are factors that can
affect the quality of photos for flexography and must be con-
sidered. Enlarging a photo excessively will soften the image
and reduce contrast.
Per FIRST (Flexographic Image Reproduction Specifications
and Tolerances) guidelines at 100 percent enlargement, 300 dpi
resolution is necessary for 133 lpi or 150 lpi line screen. Scaling
is always done before sharpening, and scales over 150 percent
should be avoided. If it is unavoidable, scaling in two steps will
be preferable to one large scale.
A grayscale strip in each shot is necessary to determine
a color neutral reference, a white-point and a black-point.
FIRST specifies that highlight settings should be between 236
and 240, and shadow settings should fall between 18 and
22. Digital files should remain in RGB, so the prepress house
tilting the plane oF sharp Focus
solution:
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FlEXo
october
2011 www.flexography.org